The central objective of the proposed research is to understand the molecular basis of protein recognition that leads to the assembly of viruses. This knowledge will help to identify steps in viral assembly mechanisms that are vulnerable to interference and control. The methodology involves use of novel static and dynamic Raman spectroscopic probes of protein structures and interactions. The specific aims are as follows: (1) Identify protein conformations and side chains that regulate subunit assembly, disassembly, viral precursor formation and genome packaging at physiological conditions. (2) Identify molecular subgroups that can be altered along the viral assembly pathway by controlled changes in cellular and/or physiological factors, such as pH, ionic composition and temperature. (3) Determine dynamics of genome transcription and replication reactions and kinetics of hydrogen-isotope (H yields D) exchange reactions in viruses, viral precursors and their components. (4) Establish new qualitative and quantitative correlations between the data of Raman spectroscopy and the structures and interactions of proteins in viruses and related macromolecular assemblies. These aims will be pursued using recently developed Raman and UV- resonance Raman methods, including: (a) polarized Raman microspectroscopy to determine side-chain orientations in viral assemblies, (b) time-resolved Raman spectroscopy to identify specific steps in viral assembly pathways, and (c) UV-resonance Raman spectroscopy for novel structural investigations of viruses and their components. Targeted for study are key virions for which complementary genetic, biochemical and structural information is available or obtainable. These include isometric viruses (HIV-l, phi6, P22, PRD1, HK97) and filamentous viruses (Ff, Pf1, Pf3, Xf, H75). The biological significance of this research program derives from the need for fundamental information about viral assembly mechanisms. Because the knowledge gained will be applicable to viruses that infect higher organisms, including humans, this research has long-term health- related benefits.